Category: Manufacturing and Bioprocessing
Purpose: The mixing is a process where there is a manipulation of a heterogeneous system with the intent to make it more homogeneous. The magnetic mixer is used in pharmaceutical industry for preparing small batch size (from few mL up to few liters). It is commonly used in development phase for performing the preliminary study where a very small amount bulk solution is needed. During the clinical phase, a medium amount of bulk solution (from few liters up to 100L) is needed for performing the clinical studies and process characterizations studies. The two systems generate different vortexes this mean different mixing force. During the proteins solution preparation an improperly seated of mixer can lead to a not complete solution homogenization or product stress with subsequent decreased product quality and/or shelf life or rejection of the batch.
Methods: The product studied in this poster is a Protein Liquid Drug Product firstly prepared in laboratory using a 5 L of glass beaker and magnetic stir bar (7 cm of length 1cm of diameter). The first GMP manufacturing was planned using 100L of disposable bag with a mechanical stirrer. In order to scale the mixing from magnetic to mechanical the following actions were considered for founding a correlation between the two mixing systems: 1) explore the potential effect of the mixing for the foaming formation, 2) explore the Dead Pockets (zone where the mixing is delayed), 3) determine the minimum mixing speed and time needed for dissolving the excipients (homogeneity study) and 4) determine the maximum mixing speed and time that prevent protein degradation (sensitivity study). The appearance of the vortex was used to define the mixing speed range as follows:
- Minimum speed when there is no evidence of turbulence and there is the presence of light vortex evident movement of the solution on the surface.
- The target speed when there is slight presence of turbulence with a evident movement of solution on the top of the liquid and presence of vortex.
- The maximum speed when there is a presence of turbulence with a strong movement of solution in the top of the liquid and there is no presence of bubbles and splashing.
The Dead Pockets (zone where the mixing is delayed) was defined performing a mixing of two liquid that have two different colors and the variation of the colors in the container was recorded and visual analyzed (camera with slow-motion program was used). The Homogeneity study was performed preparing a Sodium Chloride solution (5 g / L) and checking the osmolality at different points (sampling time each 30 sec per 10 min). The sensitivity study was performed using the protein solution checking the assay and the impurities at different time points (sampling time each 2 min per 60 min).
Results: The first study was to define the mixing range per each mixing system where there is no bubble and foaming formation using a solution with 3% of polysorbate 80.
Two different batch size (20% and 80 % of the nominal container capacity) were tested per each container at three different mixing speed (minimum, target and maximum). The results show that there are polysorbate bubbles formation with greater size in the mechanical mixer than magnetic mixer at minimum and target speed at the same volume condition. At maximum mixing speed, the mechanical mixer has generated a greater foaming formation respect magnetic mixer. The second study performed was the Dead Pockets (zone where the mixing is delayed) challenging the same batch size and speed condition of the foaming study. The results show that in the magnetic mixer the fast mixing zone is the center of the container, the mixing of the side parts is delayed instead of in the mechanic mixer the first mixing zone is the center and the top side parts of the container, and the mixing of the bottom side parts is delayed. The Homogeneity study was performed in order to define the minimum mixing speed and time needed for dissolving the excipients at maximum container volume (80%) that represent a worst case scenario. The results show that in a worst case scenario there is no difference between the two mixing system. The sensitivity study was performed in order to define the maximum mixing speed and time that prevent protein degradation. The results show that at the same conditions (volume, speed and time) the mechanic mixer is worst case respect the magnetic (more stress on the protein solution). However, caution must be taken for this study and a stability program is suggested in order to check the effect during the shelf life.
Conclusion: Different correlation studies should be considered to scaling the mixing from magnetic to mechanical: 1) Foaming, 2) Dead Pockets, 3) Homogenity and 4) Sensitivity. The optimization of the mixer parameters promotes a high product quality and/or shelf life.